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Subject[PATCH 002 of 8] md/bitmap: Remove bitmap writeback daemon.

md/bitmap currently has a separate thread to wait for writes
to the bitmap file to complete (as we cannot get a callback
on that action).
However this isn't needed as bitmap_unplug is called from
process context and waits for the writeback thread to do it's
work. The same result can be achieved by doing the waiting
directly in bitmap_unplug.


Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./drivers/md/bitmap.c | 115 ++----------------------------------------
./include/linux/raid/bitmap.h | 6 --
2 files changed, 8 insertions(+), 113 deletions(-)
diff ./drivers/md/bitmap.c~current~ ./drivers/md/bitmap.c
--- ./drivers/md/bitmap.c~current~ 2006-05-12 15:49:10.000000000 +1000
+++ ./drivers/md/bitmap.c 2006-05-12 15:55:37.000000000 +1000
@@ -7,7 +7,6 @@
* additions, Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.:
* - added disk storage for bitmap
* - changes to allow various bitmap chunk sizes
- * - added bitmap daemon (to asynchronously clear bitmap bits from disk)
*/

/*
@@ -330,14 +329,13 @@ static int write_page(struct bitmap *bit
set_page_dirty(page); /* force it to be written out */

if (!wait) {
- /* add to list to be waited for by daemon */
+ /* add to list to be waited for */
struct page_list *item = mempool_alloc(bitmap->write_pool, GFP_NOIO);
item->page = page;
get_page(page);
spin_lock(&bitmap->write_lock);
list_add(&item->list, &bitmap->complete_pages);
spin_unlock(&bitmap->write_lock);
- md_wakeup_thread(bitmap->writeback_daemon);
}
return write_one_page(page, wait);
}
@@ -621,8 +619,6 @@ static void bitmap_file_unmap(struct bit
safe_put_page(sb_page);
}

-static void bitmap_stop_daemon(struct bitmap *bitmap);
-
/* dequeue the next item in a page list -- don't call from irq context */
static struct page_list *dequeue_page(struct bitmap *bitmap)
{
@@ -648,8 +644,6 @@ static void drain_write_queues(struct bi
put_page(item->page);
mempool_free(item, bitmap->write_pool);
}
-
- wake_up(&bitmap->write_wait);
}

static void bitmap_file_put(struct bitmap *bitmap)
@@ -663,8 +657,6 @@ static void bitmap_file_put(struct bitma
bitmap->file = NULL;
spin_unlock_irqrestore(&bitmap->lock, flags);

- bitmap_stop_daemon(bitmap);
-
drain_write_queues(bitmap);

bitmap_file_unmap(bitmap);
@@ -770,6 +762,8 @@ static void bitmap_file_set_bit(struct b

}

+static void bitmap_writeback(struct bitmap *bitmap);
+
/* this gets called when the md device is ready to unplug its underlying
* (slave) device queues -- before we let any writes go down, we need to
* sync the dirty pages of the bitmap file to disk */
@@ -812,13 +806,9 @@ int bitmap_unplug(struct bitmap *bitmap)
}
}
if (wait) { /* if any writes were performed, we need to wait on them */
- if (bitmap->file) {
- spin_lock_irq(&bitmap->write_lock);
- wait_event_lock_irq(bitmap->write_wait,
- list_empty(&bitmap->complete_pages), bitmap->write_lock,
- wake_up_process(bitmap->writeback_daemon->tsk));
- spin_unlock_irq(&bitmap->write_lock);
- } else
+ if (bitmap->file)
+ bitmap_writeback(bitmap);
+ else
md_super_wait(bitmap->mddev);
}
return 0;
@@ -1126,41 +1116,12 @@ int bitmap_daemon_work(struct bitmap *bi
return err;
}

-static void daemon_exit(struct bitmap *bitmap, mdk_thread_t **daemon)
+static void bitmap_writeback(struct bitmap *bitmap)
{
- mdk_thread_t *dmn;
- unsigned long flags;
-
- /* if no one is waiting on us, we'll free the md thread struct
- * and exit, otherwise we let the waiter clean things up */
- spin_lock_irqsave(&bitmap->lock, flags);
- if ((dmn = *daemon)) { /* no one is waiting, cleanup and exit */
- *daemon = NULL;
- spin_unlock_irqrestore(&bitmap->lock, flags);
- kfree(dmn);
- complete_and_exit(NULL, 0); /* do_exit not exported */
- }
- spin_unlock_irqrestore(&bitmap->lock, flags);
-}
-
-static void bitmap_writeback_daemon(mddev_t *mddev)
-{
- struct bitmap *bitmap = mddev->bitmap;
struct page *page;
struct page_list *item;
int err = 0;

- if (signal_pending(current)) {
- printk(KERN_INFO
- "%s: bitmap writeback daemon got signal, exiting...\n",
- bmname(bitmap));
- err = -EINTR;
- goto out;
- }
- if (bitmap == NULL)
- /* about to be stopped. */
- return;
-
PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
/* wait on bitmap page writebacks */
while ((item = dequeue_page(bitmap))) {
@@ -1177,59 +1138,9 @@ static void bitmap_writeback_daemon(mdde
"failed (page %lu): %d\n",
bmname(bitmap), page->index, err);
bitmap_file_kick(bitmap);
- goto out;
+ break;
}
}
- out:
- wake_up(&bitmap->write_wait);
- if (err) {
- printk(KERN_INFO "%s: bitmap writeback daemon exiting (%d)\n",
- bmname(bitmap), err);
- daemon_exit(bitmap, &bitmap->writeback_daemon);
- }
-}
-
-static mdk_thread_t *bitmap_start_daemon(struct bitmap *bitmap,
- void (*func)(mddev_t *), char *name)
-{
- mdk_thread_t *daemon;
- char namebuf[32];
-
-#ifdef INJECT_FATAL_FAULT_2
- daemon = NULL;
-#else
- sprintf(namebuf, "%%s_%s", name);
- daemon = md_register_thread(func, bitmap->mddev, namebuf);
-#endif
- if (!daemon) {
- printk(KERN_ERR "%s: failed to start bitmap daemon\n",
- bmname(bitmap));
- return ERR_PTR(-ECHILD);
- }
-
- md_wakeup_thread(daemon); /* start it running */
-
- PRINTK("%s: %s daemon (pid %d) started...\n",
- bmname(bitmap), name, daemon->tsk->pid);
-
- return daemon;
-}
-
-static void bitmap_stop_daemon(struct bitmap *bitmap)
-{
- /* the daemon can't stop itself... it'll just exit instead... */
- if (bitmap->writeback_daemon && ! IS_ERR(bitmap->writeback_daemon) &&
- current->pid != bitmap->writeback_daemon->tsk->pid) {
- mdk_thread_t *daemon;
- unsigned long flags;
-
- spin_lock_irqsave(&bitmap->lock, flags);
- daemon = bitmap->writeback_daemon;
- bitmap->writeback_daemon = NULL;
- spin_unlock_irqrestore(&bitmap->lock, flags);
- if (daemon && ! IS_ERR(daemon))
- md_unregister_thread(daemon); /* destroy the thread */
- }
}

static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
@@ -1553,7 +1464,6 @@ int bitmap_create(mddev_t *mddev)

spin_lock_init(&bitmap->write_lock);
INIT_LIST_HEAD(&bitmap->complete_pages);
- init_waitqueue_head(&bitmap->write_wait);
bitmap->write_pool = mempool_create_kmalloc_pool(WRITE_POOL_SIZE,
sizeof(struct page_list));
err = -ENOMEM;
@@ -1613,15 +1523,6 @@ int bitmap_create(mddev_t *mddev)

mddev->bitmap = bitmap;

- if (file)
- /* kick off the bitmap writeback daemon */
- bitmap->writeback_daemon =
- bitmap_start_daemon(bitmap,
- bitmap_writeback_daemon,
- "bitmap_wb");
-
- if (IS_ERR(bitmap->writeback_daemon))
- return PTR_ERR(bitmap->writeback_daemon);
mddev->thread->timeout = bitmap->daemon_sleep * HZ;

return bitmap_update_sb(bitmap);
diff ./include/linux/raid/bitmap.h~current~ ./include/linux/raid/bitmap.h
--- ./include/linux/raid/bitmap.h~current~ 2006-05-12 15:49:10.000000000 +1000
+++ ./include/linux/raid/bitmap.h 2006-05-12 15:55:37.000000000 +1000
@@ -244,13 +244,7 @@ struct bitmap {
unsigned long daemon_lastrun; /* jiffies of last run */
unsigned long daemon_sleep; /* how many seconds between updates? */

- /*
- * bitmap_writeback_daemon waits for file-pages that have been written,
- * as there is no way to get a call-back when a page write completes.
- */
- mdk_thread_t *writeback_daemon;
spinlock_t write_lock;
- wait_queue_head_t write_wait;
struct list_head complete_pages;
mempool_t *write_pool;
};
-
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